This invention relates to sample vials and more particularly to a closure and method of assembly for a sample vial having particular utility in gas chromatography.
Closures for sample bottles such as those used for feeding samples in a gas chromatograph according to the head space method generally comprise a pot shaped metal cap with a central aperture and a septum. The septum is essentially in the form of a circular disc adapted to cover the opening of the sample bottle and is positioned within the cap. The septum is a disc of elastic material like rubber which can be pierced by a hollow needle and which reseals itself when the hollow needle is removed. Such a closure is shown in the commonly assigned Kolb et al., U.S. Pat. No. 4,248,355 issued Feb. 3, 1981 entitled "Closure for Sample Vials" which is incorporated in its entirely herein by reference.
In practice, there is a problem with such closures in that the circular septa easily falls out of the cap when the closure is turned to place it on the sample bottle. This is particularly true if a resiliently elastic annular disc having a central aperture is inserted between the metal cap and the rubber disc such as shown in U.S. Pat. No. 4,248,355.
It is also known from U.S. Pat. No. 4,248,355 that the annular disc has a smaller diameter than the metal cap and is centered therein by rounded radial projections. These projections have only the function of centering and are neither configured nor suited to hold the annular disc in the cap and secure it against falling out.
It is an object of the present invention to provide a new and improved closure for sample vials.
It is a further object of the invention to provide a closure and method of assembly which affords expeditious mounting to the sample vial.
A further object of the invention is to provide a closure for sample vials which prevents the septum from falling out of the cap during positioning of the closure on the sample vial.
Another object of the invention is to provide such a closure wherein the septum is frictionally mounted within the cap to also retain the annular disk within the cap during positioning of the closure on the sample vial.
Another object of the invention is to provide a closure for sample vials having particular utility for introducing samples into a gas chromatograph utilizing the vapor space (head space) method.
Other objects will be in part obvious and in part pointed out more in detail hereinafter.
Accordingly, it has been found that the foregoing and related objects may be attained in a closure comprising a pot shaped cap having a top wall with a central access aperture and a side wall forming a recess and a septum for covering the opening of the vial being of generally circular shape with a plurality of radially extending protrusions configured for retentive engagement with the cap side wall to retain the septum within the recess.
The method of assembling a closure on a sample vial comprises positioning the septum within the cap, securing the septum within the cap prior to mounting the cap on the sample vial and mounting the cap to the sample vial to seal the opening with the septum.